1. Field of the Invention
The invention relates generally to the analysis of performance characteristics of computer peripherals. In particular, the invention relates to a process for uniformly measuring the performance characteristics of personal computer peripherals by accommodating for variations in personal computer clock rates.
2. Brief Description of the Prior Art
In the past, a number of devices have been developed which measure the performance characteristics of computer peripherals, or targets which are typically external memory storage devices, such as Winchester disk drives, tape drives, floppy disk drives or optical drives. Analysis devices used for testing Winchester disk drives (hard disk drives), such as the Flexstar Model 5000, Wilson Model MWX 1000, or Gould Biomation Model K100-D Logic Analyzer, typically measure such characteristics as the rotational speed of the disks, seek time of the read/write head, and hard and soft error counts. A number of other similar devices exist for analyzing other types of storage systems.
Although many of the prior art analysis devices are adaptable to use with a variety of hard disks, they generally are not adaptable to use with other types of SCSI targets. In addition, such devices are typically stand alone systems, meaning they are comprises of a separate microprocessor control and associated electronics, keyboard and display, as well as meaning that they require a distinct operating system program for use. In order for an operator to use such a device, the operator must first learn the programming language that is unique to the particular device being used. Thus, aside from their inflexibility, such analysis devices are not practical for applications outside of the laboratory or manufacturing environment.
A number of peripheral manufacturers have designed their own analysis software programs, in place of the previously mentioned analysis devices, that are generally compatible with either IBM or Apple bases systems, or other odd operating based systems. Such programs are similarly capable of measuring seek times, rotation speeds, hard and soft errors, etc., but are typically limited in application to the computer system upon which it was designed. The reasoning behind the program limited utility is related to the particular computer system upon which the program was designed to run, and the clock rate of that system. In other words, a system designed to operate on one particular type of personal computer and for measuring one particular make of drive would be incompatible with many other personal computers and would most likely give incorrect or misleading performance analysis results of other makes of drives.
A significant drawback to using either the prior art programs or analysis devices concerns the variation in results that can be achieved from tests run on the same particular drive on a variety of different systems with mismatched clock rates. A number of these tests, such as the rate at which a target writes and retrieves data from storage areas within the device (the access time ), are crucial performance characteristics of the target. While hard and soft error determinations are also extremely important (and may also be determined by the preferred embodiment of the present invention), there aree a large number of currently available means for reliably making such determinations. However, there has been no previously available means for accurately determining the operational timing characteristics of a variety of drives on a variety of personal computers with different clock rates, while yielding uniform comparable results.
Although most IBM compatible personal computers outwardly appear similar, the rate at which different systems (or hosts) process information varies greatly according to the host's CPU clock frequency, which range from 4.77-10.00 MHz. Other factors, such as the length of communication cable connected to the target, create additional minor variations in the amount of time required to communicate between the target and the host system. In other words, variations in the clock rates and physical characteristics of the different hosts, upon which a particular target is tested, will result in significant variations in the amount of time required to access data, even though an identical target is used during each test. Accordingly, a manufacturer either using another company's analysis system or its own program may measure one particular average access time for its drive, while customers of the manufacture may experience much slower average access times for the same drive on their own system. Likewise, the access times of targets produced by a number of competing manufactures, as reported in specifications or sales literature, may be strikingly similar, depending on the type of test used by each manufacture, while the actual access times of each drive as tested on other analysis devices or host systems may be quite different.